Interest in health and fitness has precipitated the development of diverse exercise machines and devices including simple inclined platforms, stationary bicycles, treadmills, multi-functional exercise frames, and, most recently, stair-climbing simulators. The latter devices attempt to simulate the biomechanical activity and effect of a person raising his or her body weight from a lower step to a higher step, typically by requiring an exerciser to keep the body in the same place while the steps move, that is, by shifting body weight repeatedly from one foot to the other, optionally against variable resistance. The user's feet generally are received on moving or movable foot receiving members. Separate foot receiving members are common, either moving continuously in one direction or alternating between an upper position and a lower position. In the latter case, as one foot of the user presses down on a foot-receiving member in its upper position, that member is driven down against resistance. Generally, the second member will be rising at the same time. When the second member reaches its upper position, the user presses down on it with the other foot, raising the weight of the body or at least keeping it in the same place, and driving the second member down.
Representative examples of fairly early stair climbing devices include the types of devices disclosed in U.S. Pat. Nos. 3,497,215 (to Harrison), 3,743,283 (to Garrett), 4,340,218 (to Wilkinson), 4,687,195 (to Potts), 4,555,108 (to Monterio), and 4,726,581 (to Chang). These patents reflect the development of stair simulators, disclosing substantially static steps (the Garrett and Wilkinson patents) or an escalator-like plurality of moving steps connected to endless chains (the Harrison, Chang and Potts patents). The patent to Monterio discloses two sets of circumferential steps mounted on a rotatable member.
U.S. Pat. Nos. 3,970,302 (to McFee) and 4,496,147 (to DeCloux et al.) disclose a pair of reciprocally movable foot receiving supports carried by inclined track members. In use, the user steps on one foot support while removing weight from the second. The foot support without weight rises, while the support bearing weight descends at a rate determined by the resistance. When the downwardly traveling support reaches the end of travel, the user transfers his or her weight to the other foot and the motion of the supports reverses. The McFee and DeCloux et al. patents also disclose resistance systems, including shock absorbers or hydraulic systems, used in this type of device, and in stair simulators generally.
While the above prior art devices are useful, some of them are rather large for in-home use, they may not provide optimal muscle toning or aerobic exercise workouts, they require reciprocal leg motion, and they may be quite noisy.
U.S. Pat. No. 4,708,338 (to Potts) is fairly representative of the modern approach to solving at least some of the foregoing problems by providing a stair climbing exercise apparatus wherein a right and left pedal alternately and independently oscillate between an upper rest position and a lower position attained by the weight of or force generated by the user. As is typical in this type of machine, the pedals drive a drive sprocket in one direction through one-way clutches and are returned to their upper position by a coil spring. In this Potts device an alternator acts as a dynamic brake for providing resistance. Somewhat similar exercise machines are disclosed in U.S. Pat. Nos. 4,938,474 (to Sweeney et al.), 4,943,049 (to Lo), 4,949,993 (to Stark et al.), 5,013,031 and 5,054,770 (to Bull), 5,048,821 (to Kuo-Liang), 5,078,390 (to Hurt) and 5,033,733 (to Findlay). The Findlay apparatus includes the typical arrangement of two side-by-side steps mounted on bars pivotally connected to a frame. A cable or strap connects each step to a spring-driven pulley, and the pulleys are connected via a one-way clutch to a drive shaft. The shaft drives a multiple planetary gear arrangement, the output of which drives a rotary member having an electro-magnetic resistance element.
U.S. Pat. No. 5,039,087 (to Kuo) discloses a powered stair climber that includes pivotally mounted pedals. The climber has a gear which has two driving rods mounted at one side thereof and arranged at opposite directions. The pedals have lugs for connection to the driving rods and the gear is meshed with a worm gear on top of which there is mounted a pulley, in turn connected with a motor via a belt. FIG. 3 shows that when the motor starts rotating, the worm gear will rotate in unison therewith by means of the belt and pulley, then the gear meshed with the worm gear rotates and, since the driving rods are at opposite directions, they turn the cranks moving one pedal up and the other pedal down. Thus, an exerciser rides or stands passively on the pedals and does a stair climbing exercise when the motor is turned on. The pedals reciprocate, that is, when one moves up the other moves down and vice versa. U.S. Pat. No. 4,989,857 (to Kuo) discloses a similar stair climber with a safety speed changing device, but without a worm gear.
U.S. Pat. No. 5,007,631 (to Leao Wang) discloses a climbing exerciser having a frame body with two parallel channel bars obliquely set at each side. A sliding rod is set to slide in each bar. The sliding rods carry handles at their upper end and pedals at their lower end. The pedals include links that are connected to a cord that rotates a free wheel alternately in opposite directions.
U.S. Pat. Nos. 4,982,952 and 5,000,441 (to Shui-Mu Wang) both disclose devices including a base and an elongated prop extending upward from the base. In the earlier patent, upper and lower longitudinal slide grooves receive first left and right slide pieces (in the upper grooves) and second left and right slide pieces (in the lower slide grooves). The second slide pieces each have a foot support piece and are connected to the first slide pieces. The pieces reciprocate and resistance is provided by hydraulic cylinders. Each of the four slide pieces includes rollers B and D. In the later patent, the typical pedals disclosed in many of the above-noted patents replace the lower, second slide pieces.
U.S. Pat. No. 4,848,737 (to Ehrenfield) discloses a moving ladder exercise device including a retarder assembly (shown in FIG. 3). The retarder assembly includes an electric motor, drive shaft, worm gear assembly and clutch mechanism. FIG. 4 shows that "the chain drive sprocket 41 is forced by operator weight to rotate as shown by arrow 42. Unidirectional clutch 33 locks thereby translating torque into worm gear mechanism 32. However, no feed through to electric motor 31 can occur since the worm drive isolates the motor from the driving force. When rotation of the ladder sprocket stops or drops below the speed of the worm drive output, then clutch 33 disengages so that the motion depicted by arrow 42 cannot be transmitted to the ladder. By these means, the moving ladder is powered only by operator weight and never by the electric motor-worm drive assembly." (Ehrenfield patent, column 3, lines 31-45)
While the above-cited patents reflect refinements in the exercise machine art and progressive, general improvement in stair climbing simulators, it is clear that with current in-home stair-climbing simulating devices cost efficient manufacture, smoothness, fluidity, safety and quietness are not optimized. There is a need for a reasonably priced, biomechanically and ergonomically sound, aesthetically pleasing stair climbing simulator or "stepper" exercise machine that the exerciser enjoys using because the machine is attractive, quiet, self-prompting and has a smooth, fluid motion.